A starter motor is an electrical device used to start an internal combustion engine. Typically a very low-geared device, the starter motor is able to crank over the much larger engine by virtue of its extreme gear reduction. The starter motor is a part of a starting system consisting of the starter, a starter solenoid and the battery. As the ignition switch is turned, it sends an electrical charge to the starter solenoid. This, in turn, sends the charge to the starter motor that cranks the engine until it starts. Once the engine fires to life, the starter motor clicks off and disengage the starter ring.

The typical starter motor is composed of heavy copper wire wound around an armature. This device is placed inside of a heavy steel or aluminium case equipped with electrical brushes that contact the armature and pass the electrical charge to the heavy wire. As the electricity flows through the wire, it causes the armature to spin. A small gear is attached to the output shaft of the armature and moved in and out by means of a Bendix. The Bendix engages the small gear with the starter ring, which turns the engine as the armature turns.

Defective Symptoms

Car Won't Start

A bad starter motor is often the problem when a car's engine fails to turn. The car battery supplies the starter motor with the power to turn, or start, the engine. If the starter motor is faulty, it won't be able to utilize the power from the car battery, and the car won't start.

Starter Noise

Many times a bad starter motor makes noise--clanking, clicking or grinding--when the ignition key is turned and the starter is engaged. This type of starter noise is normally indicative of a starter motor that is worn and about to fail.

Starter Solenoid Dysfunction

A starter solenoid, which is a small mechanical attachment on top of a starter motor housing, engages and disengages the starter gear with the engine flywheel. The starter solenoid can wear out or fail, rendering the starter motor (which may still be functioning) ineffective.

Smell/Smoke

A burnt smell and/or smoke coming from a starter motor is indicative of an electrical problem with the wires and connections within a starter motor. Battery power is carried directly to a starter motor via a series of small electrical wires that attach directly to the starter solenoid. Any problem with these wires can cause a short, which can cause a burnt smell and/or smoke.

Non-Retracting Starter Gear

After a car's ignition system is activated and the starter motor engages with the engine flywheel, the starter gear is supposed to retract to its original "non-activated" position after a car starts running. A starter gear that does not retract is a sign that a starter motor is bad and needs to be replaced.

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Product AKA

Starter Motor, Engine Starter, Electric Starter

Food for Thought

Before the advent of the starter motor, engines were started by various methods including wind-up springs, gunpowder cylinders, and human-powered techniques such as a removable crank handle which engaged the front of the crankshaft, pulling on an airplane propeller, or pulling a cord that was wound around an open-face pulley.

Originally, a hand-crank was used to start engines, but it was inconvenient, difficult, and dangerous to crank-start an engine. The behaviour of an engine during starting is not always predictable. The engine can kick back, causing sudden reverse rotation. Many manual starters included a one-directional slip or release provision so that once engine rotation began, the starter would disengage from the engine. In the event of a kickback, the reverse rotation of the engine could suddenly engage the starter, causing the crank to unexpectedly and violently jerk, possibly injuring the operator. For cord-wound starters, a kickback could pull the operator towards the engine or machine, or swing the starter cord and handle at high speed around the starter pulley. Even though cranks had an overrun mechanism, when the engine started, the crank could begin to spin along with the crankshaft and potentially strike the person cranking the engine. Additionally, care had to be taken to retard the spark in order to prevent backfiring; with an advanced spark setting, the engine could kick back(run in reverse), pulling the crank with it, because the overrun safety mechanism works in one direction only.

Although users were advised to cup their fingers under the crank and pull up, it felt natural for operators to grasp the handle with the fingers on one side, the thumb on the other. Even a simple backfire could result in a broken thumb; it was possible to end up with a broken wrist, or worse. Moreover, increasingly larger engines with higher compression ratios made hand cranking a more physically demanding endeavour.

The first electric starter was installed on an Arnold (automobile), an adaptation of the Benz Velo, built 1896 in East Peckham, England by electrical engineer H. J. Dowsing

In 1911, Charles F. Kettering, with Henry M. Leland, of Dayton Engineering Laboratories Company (DELCO) invented and filed U.S. Patent 1,150,523 for the first electric starter in America. (Kettering had replaced the hand crank on NCR's cash registers with an electric motor five years earlier.)

One aspect of the invention lay in the realization that a relatively small motor, driven with higher voltage and current than would be feasible for continuous operation, could deliver enough power to crank the engine for starting. At the voltage and current levels required, such a motor would burn out in a few minutes of continuous operation, but not during the few seconds needed to start the engine. The starters were first installed by Cadillac on production models in 1912. These starters also worked as generators once the engine was running, a concept that is now being revived in hybrid vehicles. The Ford Model T relied on hand cranks until 1919; by 1920 most manufacturers included self-starters, thus ensuring that anyone, regardless of strength or physical handicap, could easily start a car with an internal combustion engine.

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